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Even if silicon is the industry normal semiconductor in most electrical products, including the solar cells that photovoltaic panels utilize to convert sun rays into energy, it is hardly the most cost-efficient product on the market. For example, the semiconductor gallium arsenide and connected compound semiconductors provide practically 2 times the efficiency as silicon in solar devices, however they are rarely utilized in utility-scale applications because of their high production value.

U. of Illinois. professors J. Rogers and X. Li investigated lower-cost methods to produce thin films of gallium arsenide which also granted usefulness in the sorts of products they can be incorporated into.

If you can reduce significantly the expense of gallium arsenide and other compound semiconductors, then you might expand their variety of applications.

Usually, gallium arsenide is transferred in a individual thin layer on a smaller wafer. Either the ideal device is made specifically on the wafer, or the semiconductor-coated wafer is break up into chips of the preferred dimension. The Illinois group chose to put in multiple levels of the material on a individual wafer, making a layered, “pancake” stack of gallium arsenide thin films.

If you grow ten layers in 1 growth, you only have to fill the wafer 1 time. If you do this in 10 growths, loading and unloading with temp ramp-up as well as ramp-down get a lot of time. If you consider exactly what is necessary for every growth – the equipment, the research, the time, the workers – the overhead saving this approach gives is a considerable expense decrease.

Next the scientists separately peel off the layers and move them. To complete this, the stacks alternate levels of aluminum arsenide with the gallium arsenide. Bathing the stacks in a solution of acid and an oxidizing agent dissolves the layers of aluminum arsenide, freeing the single small sheets of gallium arsenide. A soft stamp-like device selects up the levels, 1 at a time from the top down, for move to another substrate – glass, plastic-type or silicon, depending on the application. Then the wafer could be reused for another growth.

By executing this it’s possible to produce considerably more material more quickly and more cost efficiently. This process could generate bulk amounts of material, as compared to just the thin single-layer method in which it is typically grown.

Freeing the material from the wafer also opens the opportunity of flexible, thin-film electronics produced with gallium arsenide or different high-speed semiconductors. To make products that could conform but still retain higher efficiency, which is significant.

In a paper released on-line May 20 in the academic journal Nature, the group explains its methods and shows 3 kinds of units making use of gallium arsenide chips produced in multilayer stacks: light products, high-speed transistors and solar cells. The authors also provide a comprehensive cost evaluation.

An additional advantage of the multilayer approach is the release from area constraints, especially essential for solar cells. As the levels are removed from the stack, they may be laid out side-by-side on one more substrate to make a significantly larger surface area, whereas the standard single-layer process restricts area to the dimension of the wafer.

For photovoltaics, you need large area coverage to catch as much sunshine as possible. In an extreme situation we might grow enough layers to have 10 times the area of the standard.

Up coming, the group programs to explore more prospective device applications and other semiconductor materials that could adapt to multilayer growth.

About the Article author – Shannon Combs publishes articles for the residential solar power cost blog, her personal hobby blog focused on tips to help home owners to save energy with sun power.

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• Thin-Film Trick Makes Gallium Arsenide Devices Cheap (spectrum.ieee.org)
• Solar cells sliced and diced (nature.com)
• Spire Produces World’s Most Efficient Large Area Concentrator Solar Cell (eon.businesswire.com)
• Research hints at cheaper, more efficient photovoltaics (lightbulbs.org)

What do you think about when you consider the latest high technology gadgets? It will vary from person to person. Some might think that they’re cool. Others might think that they’re more trouble than they’re worth. Maybe you think that they’re confusing and often difficult to operate. It very much depends on your own individual viewpoint. However, it’s probably a fair bet to say that you almost certainly don’t associate the latest geeky electronic gizmo with doing your bit for the environment – even so, electronic devices can, used properly, be environmentally friendly.

Digital photo frames for example have become very popular over the last two or three years. Due to competition in the market, prices have fallen dramatically and you can now pick up perfectly serviceable examples for around about the same price that you might pay for a conventional photo frame. There are a variety of perceived benefits associated with digital frames, one of these is their capability of displaying hundreds of different photographs using a single frame.

A lot will depend upon how many photographs you take in an average year, but if you are in the habit of getting a bit snap happy then using a digital frame to display your photo collection could have a positive environmental impact. Whether you remove the need to have hard copies of photos developed at a processing lab or if you just print out less using your computer, you will wind up consuming fewer materials.

Another good, and very topical, example is the current trendy gadget – the e-book reader. These have actually been around for quite a while, but they really took off in 2009 and look set to make even more sales in 2010. The Kindle reader is currently the most popular by a long way and Sony have also established a good market presence.

125 million trees are cut down every year to provide the paper required to supply the U.S. book, magazine and newspaper industry sector. Huge amounts of water, energy and a whole host of chemicals are also consumed to feed the nation’s reading habit. On top of that, since books are a physical product they need to be delivered from the publisher to the book store – generally using road transport. The gas used by customers who drive to and from the retail outlet is also a factor in determining the carbon footprint of a typical book.

Of course, e-books do not consume large quantities of paper, ink etc. in their production. Additonally, since they are not a physical product, it’s possible to deliver them over the internet rather than by using the road transport network.

Of course, as both e-book readers and digital photo frames are themselves physical products, they do require both materials and energy for their production. They also need to be delivered to the retail outlet or direct to the end user. Nevertheless, studies have shown that, even when these materials are offset against the savings in paper, energy, ink etc. that such devices can be better for the environment (though it will depend, to a certain extent, on how many books you read or how many photos you process each year).